Letters|6 October 2015

The PRISMA Extension Statement

Jin-hui Tian, PhD; Long Ge, MD; Lun Li, PhD

Jin-hui Tian, PhD

From Evidence-Based Medicine Center of Lanzhou University and Key Laboratory of Evidence-based Medicine and Clinical Translational Research of Gansu Province, Lanzhou; and The First Clinical Medicine College of Lanzhou University, Evidence-Based Medicine Center of Lanzhou University, and Key Laboratory of Evidence-based Medicine and Clinical Translational Research of Gansu Province, Lanzhou, China.

Long Ge, MD

From Evidence-Based Medicine Center of Lanzhou University and Key Laboratory of Evidence-based Medicine and Clinical Translational Research of Gansu Province, Lanzhou; and The First Clinical Medicine College of Lanzhou University, Evidence-Based Medicine Center of Lanzhou University, and Key Laboratory of Evidence-based Medicine and Clinical Translational Research of Gansu Province, Lanzhou, China.

Lun Li, PhD

From Evidence-Based Medicine Center of Lanzhou University and Key Laboratory of Evidence-based Medicine and Clinical Translational Research of Gansu Province, Lanzhou; and The First Clinical Medicine College of Lanzhou University, Evidence-Based Medicine Center of Lanzhou University, and Key Laboratory of Evidence-based Medicine and Clinical Translational Research of Gansu Province, Lanzhou, China.

From Evidence-Based Medicine Center of Lanzhou University and Key Laboratory of Evidence-based Medicine and Clinical Translational Research of Gansu Province, Lanzhou; and The First Clinical Medicine College of Lanzhou University, Evidence-Based Medicine Center of Lanzhou University, and Key Laboratory of Evidence-based Medicine and Clinical Translational Research of Gansu Province, Lanzhou, China.

We read Hutton and colleagues' much-anticipated PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) extension statement for reporting network meta-analyses (1) with interest. We have noted that 2 items, "information sources" (item 7) and "search" (item 8), remained from the original PRISMA statement. However, we all know that searching for the evidence in network meta-analyses is more important and more complex than doing so in traditional systematic reviews and pairwise meta-analyses (2). For example, the first step in preparing a network meta-analysis is a thorough and rigorous search for previous systematic reviews and meta-analyses to ensure that the research question has not already been investigated (2). In addition, the reference lists of previously published systematic reviews and meta-analyses should be tracked to avoid missing important studies. Unfortunately, the authors of only 40% of published network meta-analyses searched the reference lists of these previous publications (3). Moreover, it is important for a specialist librarian to peer-review the quality of the searches of previous systematic reviews and meta-analyses and to determine whether the performance of the network meta-analyses is based on these previous publications. Therefore, more details of evidence searching should be needed to guide reviewers of network meta-analyses.